1. Field of the Invention
The present invention relates generally to hybrid propulsion systems, and more particularly, to a vehicle hybrid propulsion system.
2. Description of Related Art
Generally, a vehicle propulsion system comprises a startup and power generating device so as to start an engine, provide required power to electric loads during operation of the engine or charge battery of the vehicle.
Such a device is disclosed by Japanese patent publication No. 10-148142. A startup coil and a power generating coil are disposed on a stator of a motor. In the case of start, electric power is provided to the startup coil by a battery so as to use the motor as a startup device. The motor as a startup device is directly connected to a crankshaft and drives the crankshaft to rotate, thereby starting up the engine. On the other hand, the commutator and the electric brush mechanism of the motor are in contact with each other through an adjusting mechanism. After the engine is started up, the rotation speed of the engine begins to increase. The rotation of the engine further propels the rotor of the motor to rotate. When the rotation speed of the rotor reaches a predefined value, the centrifugal force of the rotor actuates the adjusting mechanism, thereby cutting off the contact between the commutator and the electric brush mechanism. Thereafter, the motor is used as a power generating device for providing electric-motive forces to electric loads of the vehicle and charging the battery.
With further development of the vehicle industry, there has been proposed an assist hybrid propulsion system that integrates an engine with an assist propulsion device for providing propulsive forces to a vehicle. As disclosed in Taiwan patent publication No. 390939, an engine startup and assist device is used to start up the engine and provide torque assist for the engine such as when the vehicle climbs or needs to deliver a large torque.
With upcoming energy crisis and environment protection concern, current widely used hybrid propulsion system introduces an automatic Stop-Go function such as disclosed by Taiwan patent No. 487779 and Japanese publication No. 58-142378. Through the automatic Stop-Go function, the engine can be stopped when the vehicle stops and the engine stays at an idle state. The engine can then be automatically ignited to start up when the vehicle starts to go, thereby saving energy and decreasing air pollution. In addition, a full-function hybrid propulsion system has been developed, which can separately utilize propulsive forces of the engine or the electric motor. Therefore, the electric motor not only can provide assist propulsive forces to the engine, it also can independently provide propulsive forces to the vehicle according to the need, and meanwhile automatically stop the engine.
Most of the hybrid propulsion systems use a torque converter or planetary gear for propulsive force connection, only a small number of hybrid propulsion systems use a plate clutch for propulsive force connection. Meanwhile, currently, only the assist hybrid propulsion system connects the electric motor to the crankshaft of the engine directly such that the electric motor and the engine can rotate coaxially and synchronously. For example, an assist hybrid propulsion system disclosed by U.S. Pat. No. 6,729, 423 B2 controls a plate clutch through oil pressure. That is, an oil hydraulic pump drives an oil hydraulic cylinder to operate the clutch plate. Compared with a system that controls the plate clutch through a lever mechanism, the assist hybrid propulsion system of the above-mentioned invention is costly, and is difficult to assemble and maintain. Further, its operation speed is slow. In addition, the design of the plate clutch is space-consuming and its assembling position is difficult to be changed. Therefore, it is difficult to realize modular manufacturing flexibility.